1. Field of the Invention
The present invention relates to a flight path display apparatus which displays a flight path on a head-up display installed in a cockpit of an aircraft.
2. Description of Related Art
Hitherto there is provided a head-up display unit which is mounted in front of a canopy of a cockpit of an aircraft and has an image combining panel through which the light from the outside view and projected information of the aircraft data are combined, so that a pilot can obtain the aircraft flight data information while seeing the outside view.
There also exists a flight path display apparatus which indicates a target flight path by superimposing on the image combining panel of the head-up display to assist the pilot in landing to an airport for example. The pilot can land safely even under low visibility due to bad weather by controlling the aircraft so as to fly along this indicated flight path. When the aircraft is a fixed wing aircraft, for example, an approach course to an airport is straight approach and an approach angle is about 3.degree..
In contrary to that, an approach course of a helicopter is not a simple straight approach but is an approach of a three-dimensional curve and an approach angle also varies considerably from 3.degree. to 12.degree. because it has to approach while avoiding slapping noise and also avoiding flight paths of other aircraft for example. It is also difficult to enlarge the area of the image combining panel of the head-up display unit because the cockpit of the helicopter is narrow and the equipment thereof must be small. Accordingly, the field of view of the existing head-up display unit is very narrow. Further, because the helicopter can change the flight direction easily, there has been a problem that the target flight path is gone outside of the image combining panel and is lost when the aircraft nose is pointing some different direction from the target flight path even if it is flying near the target flight path. Such circumstance becomes a big problem under low visibility, e.g., when the ground surface is not visible in particular.